Method of heat treating an aluminum bronze alloy



United States Patent 3,378,413 METHOD OF HEAT TREATING AN ALUMINUM BRONZE ALLOY Quentin F. Iugerson, Milwaukee, Wis., assignor to Ampco Metal, Inc., Milwaukee, Wis., a corporation of Wisconsin No Drawing. Filed Oct. 28, 1964, Ser. No. 407,229

3 Claims. (Cl. 148160) 1 This invention relates to a method of heat treating an aluminum bronze alloy, and more particularly to a method of heat treating an aluminum bronze alloy having a martensitic structure.

Aluminum bronze alloys, particularly those having from to 12% aluminum, undergo a microstructural transformation when quenched from the beta'phase to provide a martensitic structure. The martensitic structure is highly strained and is characterized by high strength and hardness and low ductility.

Normally, the alloy having a martensitic structure produced by quenching is further processed by annealing at a temperature of 1100 to 1250 R, which serves to increase the ductility of the alloy while decreasing the strength and hardness. The annealing treatment at this temperature precipitates excess aluminum of the martensitic structure resulting in the presence of secondary alpha and also stress relieves the alloy.

With the conventional copper-aluminum-iron alloy, lower annealing temperatures in the' range of 800 to 1050 F. cannot be used because the martensitic structure transforms to eutectoid which results in a more brittle alloy having reduced strength and loss of ductility.

The present invention is based on the discovery that by adding nickel, or nickel and manganese, to an aluminum bronze alloy containing from 10 to 12% aluminum, the tendency of the martensitic structure to transform to the eutectoid is substantially suppressed. The suppression or elimination of the tendency to form the eutectoid enables the alloy to be stress relieved and permits secondary alpha precipitation at a temperature in the range of 800 to 1050 F. to thereby produce an alloy having high tensile strength and high yield strength with good ductility. The aluminum bronze alloy treated in accordance with the invention compares favorably with the more expensive cast and heat treated beryllium copper alloys.

The aluminum bronze alloy to be subjected to the heat treatment of the invention has the following general formulation in weight percent:

Percent Aluminum 10 to 12 Nickel 2 to 10 Copper Balance With the addition of manganese, the alloy has the fol- In addition, from 1 to 6% iron can be substituted for a portion of the copper in the above formulations.

The alloy, as cast and before heat treatment, has the following general physical properties:

Tensile strength p.s.i 95,000 to 110,000 Yield strength ..p.s.i 45,000 to 60,000 Percent elongation percent 5 to 10 Brinell hardness 187 to 247 According to the invention, the alloy is initially heated to a temperature in the range of 1500 to 1850" F. and preferably to a temperature in the range of 1600 to 1700 F. to provide an all beta phase. With the composition of the alloy, it is necessary to heat the alloy above 1500" F. to provide the all beta phase. Heating the alloy to a temperature above 1700 F. may cause excessive grain growth unless a grain stabilizing agent is added to the composition.

The alloy is maintained at the temperature in the abovenamed range for a period of time sufficient to provide a uniform distribution of heat throughout the alloy section. The alloy is then quenched, either by water or oil, to room temperature. Quenching of the all beta phase produces a martensitic structure which is charcterized by high strength, high hardness and low ductility. Generally, the physical properties of the quenched alloy having the martensitic structure are as follows:

Tensile strength p.s.i 100,000 to 120,000 Yield strength p.s.i 55,000 to 65,000 Percent elongation "percent" 0 to 1 Brinell hardness 302 to 351 Normally, if the copper-aluminum-iron alloy is aged or stress relieved at a temperature of 800 to 1050 F., the eutectoid structure is formed which produces a brittle alloy having high hardness and strength and extremely low ductility. However, with the addition of the nickel or the addition of nickel and manganese, the alloy can be stress relieved at a temperature in the range of 800 to 1050 F. without the eutectoid formation with the result that an alloy is produced having high strength and good ductility.

The alloy is heated to a temperature of 800 to 1050 F. and preferably at a temperature in the range of 900 to 1000 F. and maintained at this temperature for a period generally of 2 to 3 hours. The resulting alloy, after cooling to room temperature, has the following physical properties:

Tensile strength p.s.i 120,000 to 140,000 Yield strength p.s.i 75,000 to 90,000 Percent elongation percent 2 to 10 Brinell hardness 248 to 302 The heat treatment of the invention can be applied to sand-cast or centrifugal-cast articles as well as extruded elements. The aluminum bronze articles heat treated in accordance with the invention have ultra high strength and good ductility and compare favorably with the more expensive cast and heat treated beryllium copper and manganese bronze. The heat treated articles can be used in most corrosive environments requiring high physical properties and is particularly adaptable for use in the marine field for propellers, shafts, gears and the like. The heat treated alloy can also be used for non-sparking safety tools that require high strength and hardness and some ductility for alloy toughness.

The following data illustrates the heat treatment of the invention as applied to sand-cast test bars:

'4 ing of (a) 10 to 12% aluminum, 1 to 6% iron, 2 to 10% nickel and the balance copper, and (b) 10 to 12% Composition Heat Treatment Properties Quench, Stress Tensile, Yield, Percent Brinell Al Fe Ni Mn Cu F. lgella iei, p.s.i. p.s.i. elong. Hardness 1 10. 24 4. 25 4. 38 0. 27 B111. 1, 650 900 124, 500 77, 500 6. 5 262 2 11. 03 4. 64 4.12 81.. 1, 650 950 138, 500 86, 500 2. 277 3 11. 7 4. 81 4- 14 Bali 1,600 1, 000 132,000 87, 500 1. 293

The following data illustrates the method of the invenaluminum, 1 to 6% iron, 2 to nickel, .01 to 5 tion as applied to centrifugal-cast test bars: manganese and the balance copper, said alloy having a Composition Heat Treatment Properties Quench, Stress Tensile, Yield, Percent Brlnell A1 Fe N 1 Mn Cu F. Igei iei, p.s.i. p.s.i. elong. Hardness 4. 92 4. 62 Bal. 675 900 136, 500 82, 250 7. 5 269 4. 28 4. 84 0. 04 Bill. 1, 600 930 135, 000 89, 500 6. 0 280 4. 63 4. 24 0.14 Bel..." 675 950 133, 250 86, 500 8. 5 262 Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. A method of heat treating an aluminum bronze al- 10y, comprising the steps of heating the aluminum bronze alloy consisting essentially of 10 to 12% aluminum, 2 to 10% nickel, and 1 to 6% iron and the balance copper to a temperature in the range of 1500 to 1850 F., quenching the alloy to room temperature, heating the al- 10y to a temperature in the range of 800 to 1050 F. to effect stress relieving of the alloy and precipitate secondary alpha phase, and cooling the alloy to room temperature.

2. The method of claim 1 wherein said aluminum bronze alloy also includes from .01 to 5% manganese.

3. A heat treated aluminum bronze alloy, consisting essentially of an alloy selected from the group consist- UNITED STATES PATENTS 2,798,826 7/1957 Klement 162 X 2,870,051 1/1959 Klement 14832 X 3,093,519 6/1963 Decker et al. 148-31 3,156,559 11/1964 Klement 75-162 3,287,180 11/1966 Eichelman et al. 148-11.5 X 3,297,497 l/l967 Eichelman et al. 148-1 1.5 X

CHARLES N. LOVELL, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,378,413 April 16, 1968 Quentin F. Ingers'on It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as' shown below:

Columns 3 and 4, TABLE 1 eight column, line 2 thereof, "138,500" should read 128,500

Signed and sealed this day of November 1969.

(SEAL) Attest;

Edward M. Fletcher, Jr. E. JR- Attesting Officer Commissioner of Patents 

1. A METHOD OF HEAT TREATING AN ALUMINUM BRONZE ALLOY, COMPRISING THE STEPS OF HEATING THE ALUMINUM BRONZE ALLOY CONSISTING ESSENTIALLY OF 10 TO 12% ALUMINUM, 2 TO 10% NICKEL, AND 1 TO 6% IRON AND THE BALANCE COPPER TO A TEMPERATURE IN THE RANGE OF 1500 TO 1850*F., QUENCHING THE ALLOY TO ROOM TEMPERATURE, HEATING THE ALLOY TO A TEMPERATURE IN THE RANGE OF 800 TO 1050*F. TO EFFECT STRESS RELIEVING OF THE ALLOY AND PRECIPITATE SECONDARY ALPHA PHASE, AND COOLING THE ALLOY TO ROOM TEMPERATURE. 